Date: Mon, 26 May 2003 02:37:05 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: Tony Maher <tonymaher@optushome.com.au> Cc: hackers@freebsd.org Subject: Re: Change request for mount_null manpage Message-ID: <3ED1E041.8ABA63A2@mindspring.com> References: <200305260836.h4Q8abgZ021438@dt.home>
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Tony Maher wrote: > I have an outstanding PR regarding nullfs > http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/28566 > > I have now removed /usr/hack nullfs mount and retested startx. > It all works fine now and I think this PR can now be closed (I'll submit > PR followup after some more testing). Also at the time of this PR I stopped > using nullfs mounts for /home because linux binaries would not work (no PR > for this). I have also retested this and everything works fine. This is because of the named pipe that's used for local clients; you can set an environment variable to disable local connections via the named pipe, but be sure to turn TCP back on, or you won't have any transport at all. 8-). Making connections via TCP will also prevent Netscape or Mozilla from eating all your memory for bitmaps, which are not cached on a window basis, so you basically "leak" them until you exit the application and it loses its connection to the X Server, if you use a local connection, which lets it use the shared memory extension. > I think the warning in mount_null man page could be toned down. Probably not a good idea, actually; in general, the reason the warning should stay is that there's still explicit cache coherency issues, when you stack a nullfs on top of an FS, and leave the original FS mount point visible in the namespace. FS stacking broke at the time of the VM and buffer cache unification, and it's only gotten more broken as time went on, unfortunately. The VM changes removed the explicit cache coherency, and replaced it with implicit, losing all the synchronization points that are still needed when you stack vnodes with real vmobject_t's; that those changes were not also made to LFS when they were made to FFS is pretty much why LFS died. -- Terry
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